Electricity-storage system, monitoring device, and power control system

ABSTRACT

An electricity-storage system  110   a  is configured to be able to charge and discharge by connecting a plug to an electrical outlet  140   a . Power discharged from the electricity-storage system  110   a  is monitored by a reverse-power monitoring device  100  and discharge from the electricity-storage system  110   a  is executed according to instruction from the reverse-power monitoring device  100 , in order to avoid reverse power flow to an electrical grid  150.

TECHNICAL FIELD

The present invention relates to electricity-storage systems.

BACKGROUND ART

In recent years, power is being generated from a variety of energysources such as thermal, hydro, wind, and solar energy sources. However,power shortages do occur for reasons such as resource insufficiency anddifficulty in ensuring a stable supply. Thus, apartments, factories,etc., may be provided with batteries to be prepared for emergencies suchas power shortage or stoppage.

Patent Literature 1 discloses a power supply system able to supply morepower to a load when a power stoppage occurs. Further, Patent Literature2 discloses a technique of supplying power by connecting a powergenerator such as a solar cell to an electrical outlet. Further, PatentLiterature 3 discloses a reverse-tidal-current-preventing systematicallyinterconnecting system that, in a power supply system, prevents adverseeffects to a load from reverse power flow and ensures rapidity ofresumed operation of a power system after power stoppage.

CITATION LIST Patent Literature [Patent Literature 1] Japanese PatentApplication Publication No. 2013-31339 [Patent Literature 2] JapanesePatent Application Publication No. 2002-354678 [Patent Literature 3]Japanese Patent Application Publication No. 2005-245136 SUMMARY OFINVENTION Technical Problem

By using batteries such as described above, power consumption can bereduced by decreasing reception of public power and electricity costscan be reduced as a result. In the future, it is conceivable that manyhomes will be provided with a battery. When considering a situation inwhich typical homes use batteries, high levels of convenience and safetyare required for such batteries.

The present invention is achieved in view of the needs described above,and has an aim of providing an electricity-storage system that is easyfor users to use and has a high level of safety.

Solution to Problem

To achieve the above aim, the electricity-storage system pertaining tothe present invention is an electricity-storage system comprising: asecondary battery; a connector that is connectable to a power linenetwork; a communicator that communicates with an external device; and acontroller that controls discharge so that, when a communicator receivesan instruction indicating discharge enablement, the power line networkis supplied power from the secondary battery via the connector.

Advantageous Effects of Invention

According to the configuration above, the electricity-storage systemperforms discharging according to instructions from an external deviceand therefore, when compared to an electricity-storage system that canfreely discharge, the possibility of reverse power flow is reduced,increasing safety when using the electricity-storage system. Further,the electricity-storage system can be used simply by connecting a plugto an electrical outlet, and therefore convenience for users isincreased.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a system diagram showing a system configuration of a powercontrol system.

FIG. 2 is a function block diagram showing function configuration of areverse-power monitoring device 100.

FIG. 3 is a function block diagram showing function configuration of anelectricity-storage system 110 a.

FIG. 4A shows electricity-storage system information. FIG. 4B shows loadinformation.

FIG. 5 is a sequence diagram showing operation of a power control systemwhen a battery is connected to a power line network.

FIG. 6 is a sequence diagram showing operation of a power control systemwhen power stoppage occurs.

FIG. 7 is a sequence diagram showing operation of a power control systemwhen power supply resumes after power stoppage.

FIG. 8 is a flowchart showing operation pertaining to the reverse-powermonitoring device 100 updating electricity-storage system information400 and load information 410.

FIG. 9 is a flowchart showing operation pertaining to discharge from abattery according to the reverse-power monitoring device 100.

FIG. 10 is a flowchart showing operation of a battery.

FIG. 11 is a function block diagram showing function configuration of areverse-power monitoring device 1100 pertaining to embodiment 2.

FIG. 12 is a function block diagram showing function configuration of anelectricity-storage system 1200 pertaining to embodiment 2.

FIG. 13 is a sequence diagram showing operation, when power stoppageoccurs, of a power control system pertaining to embodiment 2.

FIG. 14 is a flowchart showing operation of the reverse-power monitoringdevice 1100 pertaining to embodiment 2.

FIG. 15 is a flowchart showing operation of the electricity-storagesystem 1200 according to embodiment 2.

FIG. 16 is a function block diagram showing configuration of functionsof a reverse-power monitoring device when incorporated in a distributionboard.

FIG. 17 is a function block diagram showing another configurationexample of an electricity-storage system 1200.

FIG. 18 is a function block diagram showing another configurationexample of the electricity-storage system 1200.

FIG. 19 is a function block diagram showing another configurationexample of the electricity-storage system 1200.

FIG. 20 is a function block diagram showing another configurationexample of the electricity-storage system 1200.

EMBODIMENTS Embodiment 1 <Configuration>

FIG. 1 is a system diagram showing configuration of a power controlsystem. As shown in FIG. 1, the power control system includes areverse-power monitoring device 100 and electricity-storage systems 110a, 110 b connected to a power line network downstream of thereverse-power monitoring device 100. The reverse-power monitoring device100 is connected to an electrical grid 150 upstream and to adistribution panel 120 downstream. Further, aside from the electricalgrid 150 and the distribution panel 120, the reverse-power monitoringdevice 100 is also connected to a network 160. The distribution panel120 is connected to the electricity-storage systems 110 a, 110 b andloads 130 a, 130 b via the power line network and electrical outlets 140a, 140 b.

In the present embodiment, in order to simplify explanation, upstream ofthe reverse-power monitoring device 100 is referred to as the electricalgrid and downstream of the reverse-power monitoring device 100 isreferred to as the power line network. However, the power line networkis still part of the electrical grid. Here, the power line network is aclosed system, i.e. a network whose power supply passes through thereverse-power monitoring device 100 or is not received from a powercompany. Further, the power line network is also referred to as a systemrelay or simply a system.

The reverse-power monitoring device 100 has a function of issuinginstructions to discharge and stop discharge to the electricity-storagesystems 110 a, 110 b connected to the power line network and has afunction of monitoring whether or not reverse flow of power dischargedfrom the electricity-storage systems 110 a, 110 b occurs, from the powerline network to the electrical grid 150. Details of the reverse-powermonitoring device 100 are provided later.

The distribution panel 120 is composed of a main breaker 121 andbreakers 122 a, 122 b, 122 c.

Downstream of the breakers 122 a, 122 b, 122 c is lighting equipmentsuch as interior lights, the electrical outlets 140 a, 140 b forsupplying power to loads such as household appliances, etc. In FIG. 1,in addition to lighting equipment being disposed downstream of eachbreaker, the electrical outlet 140 a is disposed downstream of thebreaker 122 a and the electrical outlet 140 b is disposed downstream ofthe breaker 122 c.

The main breaker 121 and the breakers 122 a, 122 b, 122 c are typicalcircuit breakers that each have a function of breaking a circuit whenabnormal current is detected in the power line network downstream of thecircuit breaker.

The electricity-storage systems 110 a, 110 b have functions of chargingby receiving supply of power from the power line network and dischargingpower to the power line network as a result of being connected to theelectrical outlet 140 a, the electrical outlet 140 b, etc. Details ofthe electricity-storage systems 110 a, 110 b are provided later.

Each of the loads 130 a, 130 b is a household appliance, for example aPC, refrigerator, TV, vacuum cleaner, etc., that receives power supplyfrom the power line network by connection of a plug to one of theelectrical outlet 140 a and the electrical outlet 140 b. Each of theloads 130 a, 130 b has a function of sending a notification of an ID anda load capacity according to a request from the reverse-power monitoringdevice 100.

FIG. 2 is a function block diagram showing function configuration of thereverse-power monitoring device 100.

As shown in FIG. 2, the reverse-power monitoring device 100 includes apath switcher 201, a detector 202, a communicator 203, a controller 204,a charge/discharge controller 205, and a battery 206.

The path switcher 201 is inserted into a power line connecting theelectrical grid 150 and the power line network and is a switch having afunction of switching between states of physically disconnecting andconnecting the electrical grid 150 and the power line network.

The detector 202 has a function of detecting power stoppages and afunction of detecting power restoration after a power stoppage.

The detector 202 detects power stoppage and power restorationoccurrences by detecting potentials of the electrical grid 150 and thepower line network.

The detector 202 has a function of executing detection shown in table 1,below, based on system interconnection safeguards.

TABLE 1 Standard setting value (Setting range example) Setting rangeexample Protective Detection Conditions and relay class Detection leveltime controls Notes Over 115% 1 s Detects when voltage (110% to 120%)(0.5 s to 2 s) generated voltage of relay (OVR) power equipment risesabnormally, and disconnects Under 80% 1 s Detects when voltage (80% to90%) (0.5 s to 2 s) generated voltage of relay (UVR) power equipmentfalls abnormally, and disconnects Over 51.0 Hz/61.2 Hz 1 s Detects whena Grounds when frequency (50.5 Hz to (0.5 s to 2 s) frequency increasethere is reverse relay (OFR) 51.5 Hz)/(60.6 Hz is produced by power flowto 61.6 Hz) islanding, and disconnects Under 51.0 Hz/61.2 Hz 1 s Detectswhen a No operation frequency (48.5 Hz to (0.5 s to 2 s) frequencydecrease relay (UFR) 49.5 Hz)/(58.2 Hz is produced by to 59.4 Hz)islanding, and disconnects Reverse Approximately 0.5 s Detects whenGrounds when there power relay 5% of the inverter reverse power flow isno reverse power (RPR) rated output occurs due to flow. islanding, anddisconnects Islanding Corresponds to cases of low Detects when anImprovements in detection voltage interconnection islanding statedetection reliability function occurs, and by combinations ofdisconnects passive methods and active methods

Specifically, the detector 202 has, for each class in table 1, afunction of detecting power stoppage and power restoration bydetermining whether or not an actual value of the class is within arange of standard setting values based on a standard setting valuecorresponding to the class. In table 1, the setting range examplesenclosed by brackets under the standard setting values show exampleranges that can be used as standard setting values. For example, in thecase of over voltage, the detector 202 determines whether or not a statein which voltage of the electrical grid 150 is at least a predeterminedstandard voltage of 115% continues for at least one second, and when thestate of at least 115% continues for at least one second, determinesthat an abnormality, i.e. power stoppage, has occurred. Subsequently,the detector 202 notifies the controller 204 of power stoppage detectionand the controller 204, as shown under “conditions and controls”,executes disconnection via the path switcher 201. In this way thedetector 202 detects power stoppage when, for each class, the detector202 detects a state exceeding (or below) a detection level for a timeshown under “detection time”. Further, the detector 202 detects powerrestoration when determining, for each class, that an actual value iswithin a standard setting value. The frequency in table 1 is a frequencyof AC power flowing through the electrical grid 150. In table 1, settingvalues are according to the two cases: a case in which the standardfrequency of commercial power used is 50 Hz and a case in which thestandard frequency is 60 Hz. Further, reverse power flow is consideredto be power flowing from the reverse-power monitoring device 100 to theelectrical grid 150. Table 1 is a table in which setting values aredetermined in accordance with standards of commercial power in Japan,and a in a case in which power of a different frequency band to those ofJapan is used, the setting values require altering in connection withthe different frequency band.

In this way, the detector 202 performs detection of power stoppage andpower restoration using table 1.

Further, when power stoppage is detected the detector 202 communicatesthat to the controller 204 and when power restoration is detected afterpower stoppage, the detector 202 communicates that to the controller204.

The communicator 203 has a function of communicating, via the power linenetwork, between the electricity-storage systems and the loads, by usingpower line communication (PLC). The communicator 203, specifically, hasfunctions of: decoding data received from the electricity-storagesystems or the loads and transmitting it to the controller 204; andcoding data transmitted from the controller 204 and transmitting it tothe electricity-storage systems or the loads.

Further, the communicator 203 has a function of communicating, via thenetwork 160, with devices connected to the network 160, i.e. a networkother than the power line network.

The controller 204 has a function of controlling each element of thereverse-power monitoring device 100. The controller 204 has functionsprimarily for executing: information collection processing, i.e.collecting information related to devices such as theelectricity-storage systems and electrical appliances connected to thepower line network; power peak shift processing, i.e. causing theelectricity-storage systems to charge and discharge in order to controlpower consumption in the power line network; power stoppage processingwhen power stoppage occurs; and power restoration processing when powerrestoration occurs after power stoppage.

Further, the controller 204 detects whether or not there is apossibility of reverse power flow occurring, based on heldelectricity-storage system information and load information. Theelectricity-storage system information includes information about adischarge amount of each electricity-storage system connected to thepower line network. The load information includes information about loadcapacity. Details of the electricity-storage system information and theload information are provided later. The controller 204 detects thatreverse power flow is a possibility when a sum of load capacity of allloads included in the load information is less than or equal to adischarge amount of the electricity-storage systems executing discharge.In other cases, the controller 204 determines that the possibility ofreverse power flow is low.

First, the information collection processing is described below.

In order to periodically acquire information of devices connected to thepower line network, the controller 204 causes the communicator 203 totransmit response requests for requesting information of each device.Thus, with respect to the response requests, the controller 204 has afunction of receiving responses transmitted from each of theelectricity-storage systems and each of the loads and thereby updatingthe electricity-storage system information and the load information.

In a case in which the controller 204 receives a response from theelectricity-storage systems in response to a response request, thecontroller 204 extracts the electricity-storage system ID, dischargeamount, and state of charge contained in the response. Subsequently, thecontroller 204 updates the discharge amount and state of charge ofelectricity-storage system information corresponding to theelectricity-storage system ID included in the response. In a case inwhich the electricity-storage system ID included in the response is notpresent in the electricity-storage system information, the controller204 adds the electricity-storage system ID to the electricity-storagesystem information and links the discharge amount and the state ofcharge included in the response to the electricity-storage system ID.Further, when there is no response including an electricity-storagesystem ID included in the electricity-storage system information for atleast a predefined period of time after transmitting the responserequest, the controller 204 deletes the discharge amount and state ofcharge information corresponding to the electricity-storage system IDfrom the electricity-storage system information.

Further, in a case in which the controller 204 receives a response fromthe loads in response to a response request, the controller 204 extractsthe load ID and load capacity contained in the response. Subsequently,the controller 204 whether the load ID included in the response isincluded in the load information. In a case in which the load ID is notincluded in the load information, the controller 204 adds the load ID tothe load information and links the load capacity included in theresponse to the load ID. In a case in which the load ID is included inthe load information, the controller 204 does nothing. Further, whenthere is no response including a load ID included in the loadinformation for at least a predefined period of time after transmittingthe response request, the controller 204 deletes the load capacityinformation corresponding to the load ID from the load information.

Next, power peak shift processing is described below.

Power peak shift processing is processing for suppressing a peak ofpower usage in the power line network. Specifically, the controller 204acquires, via the communicator 203 and the network 160, informationrelated to transition of power usage in the power line network. Theinformation is, for example, acquired from a power company.Subsequently, from acquired information pertaining to the transition ofpower usage, the controller 204 detects whether or not there is apossibility of reverse power flow in a time period in which power usageis greatest in one day, and in a case in which the controller determinesthat there is no possibility of reverse power flow, the controller 204instructs the electricity-storage systems to discharge and suppressespower use from the power company. In a time period such as night-timewhen power used in the power line network decreases, when electricityrates are typically cheap, the controller 204 instructs theelectricity-storage systems connected to the power line network tocharge. According to this processing, peak power usage is decreased andtherefore a decrease in electricity rates can be expected according toprice schedules of electricity rates.

Finally, power stoppage processing and power restoration processing aredescribed below.

The controller 204, when notified of detection of power stoppage by thedetector 202, first executes disconnection. In other words, thecontroller 204 sets the path switcher 201 to a disconnected state.Subsequently, the controller 204 instructs, via the communicator 203,each of the electricity-storage systems connected to the power linenetwork to stop discharge. This is to temporarily set (initialize) thedischarge state in the power line network to a flat state. Subsequently,the controller 204 references the electricity-storage system informationto select an electricity-storage system having a large discharge amountas an electricity-storage system to discharge a reference voltage. In acase in which there are a plurality of identical discharge amounts, thecontroller 204 selects an electricity-storage system having a greateststate of charge among the plurality of identical discharge amounts. Thecontroller 204 then instructs, via the communicator 203, the selectedelectricity-storage system to discharge a reference voltage.Subsequently, in a case in which another electricity-storage system isconnected to the power line network, the controller instructs the otherelectricity-storage system to discharge. Here, a reference voltage is avoltage that becomes a reference for synchronizing phases of dischargewhen the other electricity-storage system discharges. For example, inJapan a reference voltage is 100 V at 50 Hz or 60 Hz.

After power stoppage, in a case in which the controller 204 is notifiedof detection of power restoration by the detector 202, the controller204 instructs, via the communicator 203, each electricity-storage systemconnected to the power line network to stop discharge. After issuing theinstruction to stop discharge, the controller 204 sets the path switcher201 to a connected state, causing electrical connection. Subsequently,the controller 204 causes the electricity-storage systems to dischargeas required, according to power peak shift processing.

The controller 204 also has a function of, when the controller 204receives a notification of detection of power stoppage from the detector202, instructing the charge/discharge controller 205 to discharge and,at a predetermined time, instructing the charge/discharge controller 205to charge.

The charge/discharge controller 205 has a function of instructing thebattery 206 to charge and discharge according to instruction from thecontroller 204.

The battery 206 has a function of receiving power from the power linenetwork via the charge/discharge controller 205 to charge a batterycell, and a function of discharging according to instruction from thecharge/discharge controller 205. The battery 206 is a power source foroperation of the reverse-power monitoring device 100 during powerstoppage, etc.

FIG. 3 is a function block diagram showing function configuration of theelectricity-storage systems 110 a, 110 b.

The electricity-storage systems 110 a, 110 b are provided with identicalconfigurations, and therefore here the configuration of theelectricity-storage system 110 a is described.

As shown in FIG. 3, the electricity-storage system 110 a includes acommunicator 301, an ACDC inverter 302, a charge controller 303, abattery 304, a DCAC inverter 305, a synchronous/asynchronous unit 306, aswitch 307, and a controller 308.

The communicator 301 has a function of communicating with thereverse-power monitoring device 100 by using PLC, via an AC plug 310 andthrough the power line network. The communicator 301 has a function ofdecoding a signal received from the reverse-power monitoring device 100via the power line network and transmitting the signal to the controller308 and a function of coding a signal transmitted from the controller308 and transmitting the coded signal to the reverse-power monitoringdevice 100 via the power line network.

The ACDC inverter 302 has a function of converting AC power suppliedfrom the power line network via the switch 307 into DC power, andoutputting the DC power to the charge controller 303.

The charge controller 303 has a function of charging the battery 304according to instruction from the controller 308.

The battery 304 is a secondary battery, for example a lithium ionbattery, having a function of receiving power supplied from the chargecontroller 303 to charge a battery cell and a function of dischargingaccording to instruction from the controller 308.

The DCAC inverter 305 has a function of converting DC power suppliedfrom the battery 304 into AC power, and outputting the AC power to thesynchronous/asynchronous unit 306.

The synchronous/asynchronous unit 306 has a function of outputting ACpower supplied from the DCAC inverter 305 to the power line network viathe AC plug 310, according to instruction from the controller 308.

The synchronous/asynchronous unit 306, upon being instructed tosynchronize and output power by the controller 308, first detects aphase of power flowing through the power line network. Subsequently, thesynchronous/asynchronous unit 306 adjusts phase of the AC power suppliedfrom the DCAC inverter 305 to match the phase detected, and then outputsthe AC power after adjusting the phase to the power line network via theswitch 307 and the AC plug 310.

On the other hand, upon being instructed to output a reference voltageby the controller 308, the synchronous/asynchronous unit 306 causes ACpower supplied from the DCAC inverter to flow “as is” to the switch 307and the AC power is outputted to the power line network via the AC plug310.

The switch 307 has a function of switching between a state of connectingthe AC plug 310 and either a charging side or a discharging side,according to instruction from the controller 308.

The controller 308 has a function of controlling each element of theelectricity-storage system 110 a.

The controller 308, upon receiving a response request from thereverse-power monitoring device 100 from the communicator 301, detects astate of charge of the battery 304 and transmits to the communicator 301a response in which the electricity-storage system ID, discharge amount,and state of charge of the electricity-storage system 110 a are linked,so that the communicator 301 transmits the response to the reverse-powermonitoring device 100.

Further, the controller 308, upon receiving a discharge stop instructionfrom the reverse-power monitoring device 100 from the communicator 301,sets the switch 307 to the charging side, i.e. connects the side of theACDC inverter 302. In a case in which the side of the ACDC inverter 302is already connected, switching of the switch 307 is not performed.

The controller 308, upon receiving a discharge instruction from thereverse-power monitoring device 100 from the communicator 301,determines whether or not the discharge instruction is a referencevoltage discharge instruction. The controller 308 determines whether ornot the discharge instruction is a reference voltage dischargeinstruction based on information included in the discharge instructionindicating whether or not the discharge instruction is a referencevoltage discharge instruction.

In a case in which the discharge instruction is a reference voltagedischarge instruction, the controller 308 instructs thesynchronous/asynchronous unit 306 that synchronization is not requiredand sets the switch 307 to the side of the DCAC inverter 305. In thisway, the electricity-storage system 110 a discharges a reference voltageto the power line network. Here, a reference voltage means AC power thatis a reference for synchronizing phase of AC power discharged by anotherelectricity-storage system.

On the other hand, in a case in which the discharge instruction is not areference voltage discharge instruction, the controller 308 instructsthe synchronous/asynchronous unit 306 that synchronization is requiredand sets the switch 307 to the side of the DCAC inverter 305.

Further, the controller 308, upon receiving a discharge stop instructionfrom the reverse-power monitoring device 100 from the communicator 301,sets the switch 307 to the charging side, i.e. connects the side of theACDC inverter 302. In a case in which the side of the ACDC inverter 302is already connected, switching of the switch 307 is not performed.

<Data>

Each type of data used in the present embodiment is described below.

FIG. 4A and FIG. 4B are data schematics of information used formonitoring occurrence of reverse power flow, held by the reverse-powermonitoring device 100.

FIG. 4A is electricity-storage system information indicating informationrelated to electricity-storage systems connected to the power linenetwork. Further, FIG. 4B is load information indicating informationrelated to loads connected to the power line network.

As shown in FIG. 4A, electricity-storage system information 400 isinformation in which an electricity-storage system ID 401, a dischargeamount 402, and a state of charge 403 are linked.

The electricity-storage system ID 401 is an identifier for identifyingan electricity-storage system connected to the power line network. Forexample, a unique device number held by an electricity-storage system, aMAC address, etc., may be used as an electricity-storage system ID.

The discharge amount 402 is information indicating a limit of dischargepossible per unit of time by the corresponding electricity-storagesystem.

The state of charge 403 is information indicating an amount of powerremaining in the corresponding electricity-storage system.

As shown in FIG. 4B, the load information 410 is information in which aload ID 411 and a load capacity 412 are linked.

The load ID 411 is an identifier for identifying a load connected to thepower line network. For example, a unique device number held by a load,a MAC address, etc., may be used as a load ID.

The load capacity 412 is information indicating a load capacity of thecorresponding load.

The above is a description of configuration of the electricity-storagesystem information 400 and the load information 410.

<Operation>

The following is a description of operation of the power control system.First, operation as a system is described, and subsequently, operationsof each of the reverse-power monitoring device 100 and theelectricity-storage system are described.

FIG. 5 is a sequence diagram showing operation of the power controlsystem when the electricity-storage system is connected to the powerline network.

As shown in FIG. 5, first, a new electricity-storage system is connectedto the power control system (step S501). In other words, a plug of thenew electricity-storage system is inserted into an electrical outlet.

The reverse-power monitoring device 100 transmits a response request toeach device connected to the power line network in order to know thestatus of each such device (step S502).

Upon receiving the response request, the electricity-storage systemacquires its own discharge amount and state of charge. Subsequently,information of the acquired discharge amount and state of charge islinked with the electricity-storage system's own electricity-storagesystem ID and transmitted to the reverse-power monitoring device 100(step S503).

Upon receiving a response from the electricity-storage system, thereverse-power monitoring device 100 updates the electricity-storagesystem information based on information received (step S504).

The reverse-power monitoring device 100 periodically transmits responserequests (step S505).

An electricity-storage system that receives the response requestacquires its own discharge amount and state of charge. Subsequently,information of the acquired discharge amount and state of charge islinked with the electricity-storage system's own electricity-storagesystem ID and transmitted to the reverse-power monitoring device 100(step S506).

Upon receiving a response from the electricity-storage system, thereverse-power monitoring device 100 updates the electricity-storagesystem information based on information received (step S507).

In this way, the reverse-power monitoring device 100 updates heldelectricity-storage system information and can cause anelectricity-storage system connected to the power line network to chargeand discharge as appropriate. Although not shown in FIG. 5, aside fromthe electricity-storage system, each load connected to the power linenetwork also transmits information of load capacity in response to theresponse request, and thus the reverse-power monitoring device 100updates load information.

FIG. 6 is a sequence diagram showing operation of the power controlsystem when power stoppage occurs.

As shown in FIG. 6, the reverse-power monitoring device 100 detectspower stoppage (step S601).

In such a case, the reverse-power monitoring device 100 executesdisconnection (step S602) and subsequently instructs eachelectricity-storage system connected to the power line network to stopdischarge (step S603).

The electricity-storage systems 110 a, 110 b each receive theinstruction to stop discharge and when discharge is being executed, stopdischarging (Step S605, Step S606).

The reverse-power monitoring device 100, after instructing to stopdischarge, selects an electricity-storage system to discharge areference voltage (step S607). In this example the electricity-storagesystem 110 a is selected.

Subsequently, the reverse-power monitoring device 100 instructs theselected electricity-storage system to discharge a reference voltage(step S608). Here, the reverse-power monitoring device 100 instructs theelectricity-storage system 110 a to discharge a reference voltage.

The electricity-storage system 110 a that has received the instructionstarts discharging a reference voltage to the power line network (stepS609).

The reverse-power monitoring device 100 then instructs theelectricity-storage system 110 b to discharge (step S610).

The electricity-storage system 110 b that has received the instructionsynchronizes with a reference voltage being discharged by theelectricity-storage system 110 a and discharges (step S611).

Thus, when power stoppage occurs, the power control system temporarilystops discharging in a case in which an electricity-storage system isdischarging, and after executing disconnection, causes discharge from anelectricity-storage system to compensate for the power stoppage in a waythat does not cause reverse power flow.

FIG. 7 is a sequence diagram showing operation of the power controlsystem when power restoration occurs after power stoppage.

After power stoppage, the reverse-power monitoring device 100 detectsrestoration of power in the electrical grid 150 (step S701).

Upon detecting power restoration, the reverse-power monitoring device100 first instructs each electricity-storage system to stop discharge(step S702).

The electricity-storage systems 110 a, 110 b each receive theinstruction to stop discharge and when discharge is being executed, stopdischarging (Step S703, Step S704).

After outputting the instruction to stop discharge, the reverse-powermonitoring device 100 causes the path switcher 201 to connect so thatpower supply is received (step S705).

According to this power restoration processing, the power control systemcan restore power from a state of power stoppage and return to normaloperation.

The following describes operations of the reverse-power monitoringdevice 100 and the electricity-storage system 110 a for implementing thesequences shown in FIGS. 5-7.

First, operation of the reverse-power monitoring device 100 is shown byusing FIG. 8 and FIG. 9.

FIG. 8 is a flowchart showing an information collection processingoperation pertaining to the reverse-power monitoring device 100 updatingthe electricity storage system information 400 and the load information410.

The controller 204 periodically instructs the communicator 203 totransmit a response request in order to collect information about theelectricity-storage systems and loads connected to the power linenetwork.

The communicator 203 receives a response from each electricity-storagesystem and load connected to the power line network (step S802).

Upon receiving a response via the communicator 203, the controller 204first, in a case in which electricity-storage system information ispresent and corresponds to an electricity-storage system ID included inthe response from an electricity-storage system, updates a state ofcharge corresponding to the electricity-storage system information witha value of a state of charge included in the response (step S803).

In a case in which the response is from an electricity-storage systemand includes an electricity-storage system ID that is not present in theelectricity-storage system information 400 (YES at step S804), theelectricity-storage system ID is added to the electricity-storage systeminformation 400 and linked to a discharge amount and a state of chargeincluded in the response, updating the electricity-storage systeminformation 400 (step S805).

Next, the controller 204 checks whether or not there is anelectricity-storage system that has not responded for at least apredetermined length of time according to the electricity-storage systeminformation (step S806).

In a case in which there is an electricity-storage system ID in theelectricity-storage system information for an electricity-storage systemthat has not responded (YES at step S806), the controller 204 deletesthe electricity-storage system ID and linked discharge amount and stateof charge of the electricity-storage system from the electricity-storagesystem information (step S807). In a case in which anelectricity-storage system ID for an electricity-storage system that hasnot responded is not present in the electricity-storage systeminformation, i.e., a response is received from every electricity-storagesystem corresponding to the electricity-storage system IDs included inthe electricity-storage system information 400 (NO at step S806),processing proceeds to step S808.

The controller 204 then determines, with respect to a responsetransmitted from a load in response to the response request, whether ornot a load ID included in the response is included in the loadinformation (step S808).

In a case in which a load ID not present in the load information isincluded in the response (YES at step S808), the controller 204 links aload capacity included in the response to the load ID and records theload ID and the load capacity in the load information (step S809).

Next, the controller 204 checks whether or not there is a load that hasnot responded for at least a predetermined length of time according tothe load information (step S810).

In a case in which there is a load ID in the load information for a loadthat has not responded (YES at step S810), the controller 204 deletesthe load ID and linked load capacity of the load from the loadinformation (step S811). In a case in which a load ID for a load thathas not responded is not present in the load information, i.e., aresponse is received from every load corresponding to the load IDsincluded in the load information 410 (NO at step S810), processingreturns to step S801.

The above is a description of information collection processing, whichthe reverse-power monitoring device 100 periodically executes.

FIG. 9 is a flowchart showing operation of power control processingaccording to the reverse-power monitoring device 100.

As shown in FIG. 9, the reverse-power monitoring device 100 executespower peak shift processing (step S901). As described above, power peakshift processing is processing for reducing a total amount of electricalpower used by the power line network and is executed based oninformation related to power use trends in the power line networkacquired by the communicator 203 via the network 160.

The reverse-power monitoring device 100 executes reverse power detectionprocessing. The reverse-power monitoring device 100 determines thatthere is a possibility of reverse flow in a case in which a total loadcapacity of all loads included in the load information does not exceed atotal discharge amount of electricity-storage systems executingdischarge included in the electricity-storage system information (stepS902).

In a case in which a possibility of reverse flow is positivelydetermined (YES at step S902), the controller 204 transmits a dischargestop instruction to at least one electricity-storage system via thecommunicator 203 (step S903). In a case in which a low possibility ofreverse flow is determined (NO at step S902), the controller 204transmits a discharge instruction to at least one electricity-storagesystem via the communicator 203 (step S904).

In a case in which the detector 202 of the reverse-power monitoringdevice 100 detects a power stoppage (step S905), the detector 202notifies the controller 204 of the power stoppage detection. Uponreceiving the notification the controller 204 executes disconnection viathe path switcher 201 (step S906).

Subsequently, the controller 204 transmits a discharge stop instructionto each of the electricity-storage systems via the communicator 203(step S907).

After transmitting the discharge stop instruction, the controller 204selects an electricity-storage system to discharge a reference voltageduring power stoppage (step S908). The controller 204 refers to theelectricity-storage system information and selects theelectricity-storage system having the highest discharge amount tocontrol. In a case in which there is a plurality of electricity-storagesystems having the highest discharge amount, the controller 204 selectsan electricity-storage system having a greatest state of charge amongthe plurality.

Subsequently, via the communicator 203, the controller 204 instructs theselected electricity-storage system to discharge a reference voltage(step S909). The electricity-storage system that receives a referencevoltage discharge instruction discharges power asynchronously to thepower line network.

The controller instructs electricity-storage systems other than theselected electricity-storage system to simply discharge (step S910). Theelectricity-storage system that receives a normal discharge instructiondischarges power to the power line network that is synchronized to thephase of AC power flowing through the power line network.

After power stoppage occurs, the detector 202 detects potentials of theelectrical grid 150 to detect whether or not power restoration hasoccurred (step S912). Upon detecting power restoration (YES at stepS912), the detector 202 notifies the controller 204 of the powerrestoration.

Upon receiving the notification of power restoration, the controller 204transmits, via the communicator 203, an instruction to each of theelectricity-storage systems to stop discharge (step S913). Theelectricity-storage systems each receive the instruction to stopdischarge and when discharge is being executed, stop discharging.

Subsequently, the controller 204 causes the path switcher 201 toconnect, thereby causing power to flow from the electrical grid 150 tothe power line network (step S914).

The above is a description of processing pertaining to power controlaccording to the reverse-power monitoring device 100. The processingshown in FIG. 9 is repeatedly executed.

FIG. 10 is a flowchart showing operation of an electricity-storagesystem. Description is of operation of the electricity-storage system110 a, but the electricity-storage system 110 b operates the same way.

The communicator 301 receives a signal from the reverse-power monitoringdevice 100 via an AC plug by using PLC.

The controller 308, in a case in which a signal received from thecommunicator 301 is a response request (YES at step S1001), acquires adischarge amount and state of charge of the battery 304 (step S1002).Subsequently, the controller 308 causes the communicator 301 to transmita response in which the electricity-storage system ID, the dischargeamount, and the state of charge of the electricity-storage system arelinked (step S1003).

The controller 308, in a case in which a signal received from thecommunicator 301 is a discharge instruction (YES at step S1004),determines whether or not the discharge instruction is a referencevoltage discharge instruction (step S1005). The determination isperformed based on a flag included in the discharge instruction thatindicates whether or not the discharge instruction is a referencevoltage discharge instruction.

In a case in which the discharge instruction is a reference voltagedischarge instruction (YES at step S1005), the controller 308 outputs aninstruction for asynchronous output to the synchronous/asynchronous unit306. Subsequently, the switch 307 switches to the side of the DCACinverter 305. In this way, a reference voltage is outputted to the powerline network.

In a case in which the discharge instruction is not a reference voltagedischarge instruction (NO at step S1005), the controller 308 outputs aninstruction for synchronous output to the synchronous/asynchronous unit306. Subsequently, the switch 307 switches to the side of the DCACinverter 305. The synchronous/asynchronous unit 306 detects the phase ofAC power flowing to the power line network and adjusts the phase of ACpower outputted from the DCAC inverter 305 to synchronize, i.e. matchphase, with power flowing to the power line network, in order to outputthe AC power to the power line network. In this way, supply of power tothe power line network from the electricity-storage systems isperformed, power insufficiency can be compensated for, and when a largeamount of power is being used a portion of the power supplied from apower company can be reduced.

In a case in which a signal received from the communicator 301 is adischarge stop instruction (YES at step S1008), the controller 308causes the switch 307 to switch to the side of the ACDC inverter 302(step S1009) and processing returns to step S1001.

The above is a description of operation of the electricity-storagesystem 110 a.

<Summary>

As indicated in embodiment 1, each of the electricity-storage systemsdoes not discharge unless it receives a discharge instruction from thereverse-power monitoring device 100, and therefore the possibility ofreverse power flow is as low as possible. This is because thereverse-power monitoring device 100 detects the presence and absence ofthe possibility of reverse power flow occurring and when determiningthat there is a possibility of reverse power flow a dischargeinstruction is not performed, thus reverse power flow can be prevented.

Embodiment 2

According to embodiment 1, above, the reverse-power monitoring device100 detects power stoppage. According to embodiment 2, a case isdescribed in which the electricity-storage systems, not thereverse-power monitoring device, detect power stoppage.

<Configuration>

FIG. 11 is a function block diagram showing configuration of areverse-power monitoring device 1100 pertaining to embodiment 2.

The reverse-power monitoring device 1100 includes a detector 1102instead of the detector 202.

The detector 1102 has a function, unlike the detector 202 of embodiment1, of only detecting power restoration and not detecting power stoppage.In a case in which power restoration is detected, the detector 1102transmits an indication thereof to the controller 1104.

The controller 1104 has functions approximately the same as those of thecontroller 204 indicated in embodiment 1, with a point of differencebelow.

The controller 1104 is not notified of power stoppage from the detector1102 and is notified by reception of power stoppage informationtransmitted from the electricity-storage system via the communicator203.

In a case in which power stoppage information is transmitted to thecontroller 1104 from the communicator 203, the controller 1104 executespower stoppage processing in the same way as the controller 204. Inother words, the controller 1104 executes disconnection via the pathswitcher 201 and subsequently instructs each of the electricity-storagesystems to stop discharge via the communicator 203. The controller 1104then selects an electricity-storage system to discharge a referencevoltage to instruct the selected electricity-storage system to dischargea reference voltage.

FIG. 12 is a function block diagram showing configuration of anelectricity-storage system 1200 pertaining to embodiment 2. As shown inFIG. 12, the electricity-storage system 1200 includes a communicator1201, a switch 1202, a power stoppage detector 1203, asynchronous/asynchronous unit 1204, a bi-directional inverter 1205,charge/discharge controller 1206, a battery 1207, and a controller 1208.

The communicator 1201 has a function of executing communication with thereverse-power monitoring device 1100 via an AC plug 1210, an electricaloutlet, and the power line network.

The switch 1202 has a function of switching on and off according toinstruction from the controller 1208.

The power stoppage detector 1203 has a function of detecting potentialsof the power line network to determine whether or not power stoppage isoccurring. In a case in which power stoppage is detected, the powerstoppage detector 1203 has a function of transmitting an indicationthereof to the controller 1208.

The synchronous/asynchronous unit 1204, during charging, allows power toflow to the bi-directional inverter 1205. Further, during discharging,when there is an instruction for synchronization from the controller1208, the synchronous/asynchronous unit 1204 adjusts a phase of AC powersupplied from the bi-directional inverter 1205 according to thenotification of the phase of AC power from the controller 1208 thenoutputs to the power line network via the power stoppage detector 1203and the switch 1202. When instructed to output a reference voltage, thesynchronous/asynchronous unit 1204 outputs AC power supplied from thebi-directional inverter 1205 “as is” to the power line network via thepower stoppage detector 1203 and the switch 1202.

The bi-directional inverter 1205 has a function of converting AC powerto DC power and a function of converting DC power to AC power. Thebi-directional inverter 1205, during charging, converts AC power flowingfrom the synchronous/asynchronous unit 1204 to DC power and outputs theDC power to the charge/discharge controller 1206 according toinstruction from the controller 1208. Further, when discharging, thebi-directional inverter 1205 converts DC power transmitted from thecharge/discharge controller 1206 to AC power and outputs the AC power tothe synchronous/asynchronous unit 1204.

The charge/discharge controller 1206 has a function of charging thebattery 1207 by receiving DC power from the bi-directional inverter 1205and a function of outputting DC power received from the battery 1207 tothe bi-directional inverter, both functions performed in accordance withinstruction from the controller 1208.

The battery 1207 has a function of executing charging and dischargingaccording to instruction from the charge/discharge controller 1206.

<Operation>

FIG. 13 is a sequence diagram showing operation, when power stoppageoccurs, of the power control system pertaining to embodiment 2.

As shown in FIG. 13, when power stoppage occurs, each of theelectricity-storage systems detects power stoppage (steps S1301, S1302).

An electricity-storage system 1200 a that has detected the powerstoppage transmits power stoppage information that indicates theoccurrence of power stoppage to the reverse-power monitoring device 1100(step S1303). Likewise, an electricity-storage system 1200 b alsotransmits power stoppage information to the reverse-power monitoringdevice 100 (step S1304).

The reverse-power monitoring device 1100 that has received the powerstoppage information sets the path switcher 201 to disconnect, therebydisconnecting (step S1305).

The following processing is identical to that described in FIG. 6 ofembodiment 1, and therefore omitted here.

FIG. 14 is a flowchart showing operations of the reverse-powermonitoring device 1100 pertaining to embodiment 2. Description ofoperations in common with the reverse-power monitoring device 100pertaining to embodiment 1 is omitted, and only operation unique toembodiment 2 are described here. Thus, in FIG. 14, processing in commonwith embodiment 1 has the same reference signs as in FIG. 9.

As shown in FIG. 14, operation of the reverse-power monitoring device1100 differs from embodiment 1 in the processing of step S1406. Thecontroller 1104 detects occurrence of power stoppage by whether or notpower stoppage information is received from the communicator 203 (stepS1406).

When power stoppage information is received (step S1406), the controller1204 treats that as a trigger and executes disconnection (step S907),i.e. sets the path switcher 201 to the disconnected state.

FIG. 15 is a flowchart showing operations of the electricity-storagesystem 1200 pertaining to embodiment 2.

As shown in FIG. 15, when the power stoppage detector of theelectricity-storage system 1200 detects power stoppage (YES at stepS1510) an indication of the detection is transmitted to the controller308.

The communicator 1201 receives a signal from the reverse-powermonitoring device 1100 via the AC plug 1310 by using PLC.

The controller 1208, in a case in which a signal received from thecommunicator 1201 is a response request (YES at step S1501), acquires adischarge amount and state of charge of the battery 1207 (step S1502).Subsequently, the controller 1208 causes the communicator 1201 totransmit a response in which the electricity-storage system ID, thedischarge amount, and the state of charge of the electricity-storagesystem are linked (step S1503).

The controller 1208, in a case in which a signal received from thecommunicator 1201 is a discharge instruction (YES at step S1504),determines whether or not the discharge instruction is a referencevoltage discharge instruction (step S1505). The determination isperformed based on a flag included in the discharge instruction thatindicates whether or not the discharge instruction is a referencevoltage discharge instruction.

In a case in which the discharge instruction is a reference voltagedischarge instruction (YES at step S1505), the controller 1208 outputsan instruction for asynchronous output to the synchronous/asynchronousunit 1204. Subsequently, the switch 1202 is set to a connected state. Inthis way, a reference voltage is outputted to the power line network.

In a case in which the discharge instruction is not the referencevoltage discharge instruction (NO at step S1505), the controller 1208outputs an instruction for synchronous output to thesynchronous/asynchronous unit 1204. Subsequently, the switch 1202 is setto a connected state. The bi-directional inverter 1205 receives DC powerfrom the battery 1207 and converts it to AC power. Thesynchronous/asynchronous unit 1204 detects the phase of AC power flowingto the power line network and adjusts the phase of AC power outputtedfrom the bi-directional inverter 1205 to synchronize, i.e. match phase,with power flowing to the power line network, in order to output the ACpower to the power line network. In this way, supply of power to thepower line network from the electricity-storage systems is performed,power insufficiency can be compensated for, and when a large amount ofpower is being used a portion of the power supplied from a power companycan be reduced.

In a case in which a signal received from the communicator 1201 is adischarge stop instruction (YES at step S1508), the controller 1208 setsthe switch 1202 to a disconnected state (step S1509) and processingreturns to step S1501.

When the power stoppage detector 1203 detects power stoppage (YES atstep S1510), the power stoppage detector 1203 notifies the controller1208 of the detection.

Thus, the controller 1208, in accordance with the notification,transmits power stoppage information indicating that power stoppage isoccurring to the reverse-power monitoring device 1100 via thecommunicator 1201 (step S1511). According to transmission of the powerstoppage information, disconnection is executed and reverse power flowcan be prevented.

The above is a description of operation of the electricity-storagesystem 1200.

<Summary>

According to embodiment 2, detection of power stoppage is performed bythe electricity-storage system and, in addition to prevention of reversepower flow during power stoppage, power from the electricity-storagesystem can be supplied to the power line network during power stoppage.

<Supplement>

The power control system pertaining to the present invention accordingto the embodiments is described above, but the present invention is notlimited to this description. The following describes modifications thatare included in the concept of the present invention.

(1) According to an embodiment above, the reverse-power monitoringdevice 100 includes the path switcher 201 internally. However, as longas the path switcher 201 is inserted into a power line for supplyingpower to the power line network from the electrical grid, thereverse-power monitoring device 100 may be disposed as an external unit.In such a case, the reverse-power monitoring device 100 includes aninterface for outputting instructions pertaining to path switching andsets the path switcher 201 to connect.

(2) According to an embodiment above, the detector 202 detects thatthere is a possibility of reverse power flow when a total of loadcapacity of the loads connected to the power line network is not morethan a total of discharge amounts of the electricity-storage systemsexecuting discharge. However, other configurations are possible as longas determination of the possibility of reverse power flow can be made.

For example, the detector 202 may determine that there is a possibilityof reverse power flow when a total of load capacity is not more than athreshold at least a certain value lower than a total of dischargeamounts of the electricity-storage systems executing discharge.According to such a configuration, the possibility of reverse power flowcan be reduced by a further margin over the configuration according toembodiment 1, and therefore reliability of detection of reverse powerflow can be increased and safety of the system can be increased.

Alternatively, instead of the detector 202 using the electricity-storagesystem information and the load information, the power line network maybe provided with nodes, voltage may be detected at each node and whetheror not there is a possibility of reverse power flow may thereby bedetected.

Specifically, voltage may be detected at key locations in the power linenetwork (for example, at branch points of the power line network or atterminals downstream of each breaker). A connecting line may be providedfrom the reverse-power monitoring device directly to each node so thatthe reverse-power monitoring device detects voltage, or each node may beprovided with a voltage detection device and voltage values detected bythe voltage detection device may be transmitted to the reverse-powermonitoring device.

Thus, an upper limit of voltage is determined for each node, and whetheror not there is a possibility of reverse power flow is determinedaccording to whether or not a detected voltage value exceeds the upperlimit (or a threshold lower than the upper limit). In a case in which adetected voltage value is determined to exceed a corresponding upperlimit, the reverse-power monitoring device determines that reverse powerflow is a possibility and causes the electricity-storage systems to stopdischarge. At this time, the reverse-power monitoring device mayinstruct the electricity-storage systems to execute charging. Further,in a case in which the possibility of reverse power flow is low, thereverse-power monitoring device may instruct the electricity-storagesystems to discharge.

(3) According to embodiment 2, after the electricity-storage systemdetects power stoppage, the electricity-storage system waits forinstruction from the reverse-power monitoring device to stop discharge,but other configurations are possible and a method of stopping dischargemay be configured as follows. When the electricity-storage system has afunction of detecting power stoppage as in embodiment 2, theelectricity-storage system need not wait for instruction from thereverse-power monitoring device and may stop discharging. In this way,the possibility of reverse power flow can be further decreased.

(4) According to embodiment 2, each of the electricity-storage systemsdetects power stoppage and notifies the reverse-power monitoring device,but other configurations are possible as long as power stoppage can bedetected.

In a case in which the electricity-storage systems are connected to thepower line network, any one of the electricity-storage systems maydetect power stoppage and notify the reverse-power monitoring device.Further, at such time, the electricity-storage system that detectedpower stoppage may notify not only the reverse-power monitoring devicebut also the electricity-storage systems other than theelectricity-storage system. Thus, electricity-storage systems thatreceive the notification may be configured to stop discharge if they aredischarging.

(5) According to an embodiment above, the reverse-power monitoringdevice and the electricity-storage systems communicate according to PLC,but other communication methods (protocols) may be used as long as boththe reverse-power monitoring device and the electricity-storage systemscan transmit information.

For example, the reverse power monitoring device and theelectricity-storage systems may be provided with wireless communicatorsand information may be transmitted via wireless communication based on awireless communication standard such as Wi-Fi (registered trademark).

(6) According to an embodiment above, the discharge instruction by thecontroller 204 during power stoppage is executed after temporarilyexecuting a discharge stop instruction with respect to theelectricity-storage systems.

At such time, the controller 204 of the reverse-power monitoring device100 may cause the detector 202 to detect potentials of the power linenetwork and the controller 204 may instruct discharge after detectionthat discharge from the electricity-storage systems has stopped.

Further, in power restoration processing, the controller 204 may causethe path switcher 201 to connect after executing a discharge stopinstruction and after confirming that discharge from theelectricity-storage systems has stopped. Confirmation may be obtained bythe electricity-storage systems transmitting discharge stop informationindicating that discharge has stopped and may be obtained by causing thedetector 202 to detect potentials of the power line network.

(7) According to an embodiments above, although not explicitlyspecified, the controller 204 may also execute disconnection via thepath switcher 201 when the controller 204 determines that there is apossibility of reverse power flow. In such a case, the controller 204may execute connection via the path switcher 201 when the controllerdetermines that the possibility of reverse power flow is low. In thisway, safety of the power control system can be further increased.

(8) According to an embodiment above, although not explicitly specified,responses from the electricity-storage systems and the loads in responseto a response request may, for example, be controlled by thereverse-power monitoring device 100 by a response timing specified inthe response request in order to avoid interference on the power linenetwork. Further, for example, configuration may be such that even wheninterference occurs a response arrives at the reverse-power monitoringdevice by causing responses to be re-transmitted. This can beimplemented by, for example, transmitting an acknowledgement signalindicating that a signal is received from a signal reception side foreach signal transmitted, and in a case that an acknowledgement signal isnot received the signal is re-transmitted.

(9) According an embodiment above, discharge pertaining to power peakprocessing is executed at a timing at which most power is used in thepower line network. However, the reverse-power monitoring device maycause discharge from an appropriate electricity-storage system at othertimings to reduce usage of power supplied from a power company.

(10) Although not explicitly described in an embodiment above, thereverse-power monitoring device 100 may further include a home energymanagement system (HEMS) that controls loads. In other words, thereverse-power monitoring device 100 may include a configurationsuppressing possibility of reverse power flow by executing instructionsto increase and decrease power consumption by loads.

(11) Although not explicitly described in an embodiment above theelectricity-storage systems 110 a, 110, 1200 may further include aterminal for outputting power, i.e. an electrical outlet. Instead of viaa power line network by insertion of a plug of another electrical deviceinto the electrical outlet, the electrical outlet may be configured todirectly supply power from the electricity-storage system.

(12) According to an embodiment above, each load transmits loadinformation in response to a response request. However, depending on theload, a case may occur in which the load does not have a function oftransmitting load information.

In such a case, a power monitoring device may be provided to an outputat a load side to monitor operation of a power conditioner, and a powersource disconnection circuit may be provided to handle protection fromsudden load fluctuation, etc.

(13) According to an embodiment above, the electrical outlets 140 a, 140b, and the AC plugs 310, 1210 are provided as mechanisms for connectingthe electricity-storage systems to the power line network. However, aslong as power supply can be received and transmission can be executed,other forms of connector may be used.

(14) According to an embodiment above, the reverse-power monitoringdevice 100 is configured to detect whether or not a newelectricity-storage system is connected to the power line networkaccording to a response from the electricity-storage system. However, asa method of causing the reverse-power monitoring device 100 to recognizea new electricity-storage system, other configurations are possible.

For example, the electricity-storage system may be provided with abutton that can be pressed by a user. Thus, upon receiving the press ofthe button when the electricity-storage system is connected, thecontroller 204 may cause transmission of information including theelectricity-storage system ID, the discharge amount, and the state ofcharge. The reverse-power monitoring device 100 that receives theinformation adds the electricity-storage system ID to theelectricity-storage system information and updates theelectricity-storage system information. According to such aconfiguration, the reverse-power monitoring device 100 may be caused torecognize existence of a new electricity-storage system.

(15) According to an embodiment above, an example is described in whichdischarge from the electricity-storage system is executed according toinstruction from the reverse-power monitoring device 100, but otherconfigurations are possible. For example, a configuration is possible inwhich the electricity-storage system requests permission to dischargefrom the reverse-power monitoring device, the reverse-power monitoringdevice provides permission in response to the request, and discharge isperformed. In such a case, the request to discharge from theelectricity-storage system may be outputted at any timing. For example,the electricity-storage system may store a predefined schedule fortiming of transmission of the request and perform requests according tothe schedule. The schedule may be inputted by a user, and theelectricity-storage system may be connected to the network 160, acquireinformation indicating usage of power in the power line network, andcreate the schedule according to the information.

(16) Here, alternative configurations to the configurations of theelectricity-storage systems indicated in the embodiments above aredescribed.

FIGS. 17 to 20 show alternative configurations of theelectricity-storage system 1200 and examples supplied with powerdirectly from photovoltaics (PV), which are power generators, or via aPV power conditioner.

FIG. 17 shows a first alternative configuration. As shown in FIG. 17,the electricity-storage system 1200 further includes an AC/DC converter1700.

As shown in FIG. 17, the AC/DC converter 1700 is connected to a PV powerconditioner 1701 and a PV 1702 via the PV power conditioner 1701.

The PV 1702 is a photovoltaic power generator that generates power byreceiving sunlight. The PV 1702 is also called a solar power generator.The PV 1702 receives sunlight, generates power, and transmits thegenerated power to the PV power conditioner 1701.

The PV power conditioner 1701 is a power conditioner for photovoltaicpower. The PV power conditioner 1701 has a function of adjustingreceived power to AC power that the electricity-storage system 1200 canuse. The PV power conditioner 1701 outputs AC power after adjustment tothe electricity-storage system 1200.

The AC/DC converter 1700 receives supply of AC power adjusted by the PVpower conditioner 1701, converts it into DC power, and applies the DCpower thus obtained to the charge/discharge controller 1206. Thus, thecharge/discharge controller 1206 may be configured to supply the DCpower received from the AC/DC converter 1700 to the battery 1207 toexecute charging.

Thus, the electricity-storage system 1200 need not rely only on powerfrom the power line network to charge. Even when power supply ceasesfrom one source, power supply can be received from the other source andcharging can be executed, and therefore convenience of theelectricity-storage system 1200 is increased.

Alternatively, the electricity-storage system 1200 indicated in FIG. 17may be configured as shown in FIG. 18. The electricity-storage system1200 shown in FIG. 18 is provided with a DC/DC converter 1800 instead ofthe AC/DC converter 1700.

When configured as shown in FIG. 18, a PV power converter is notrequired, the DC/DC converter 1800 receives DC power directly from a PV1802 and converts the received DC power into DC power of a voltage andcurrent that can be used to charge the battery 1207. The DC/DC converter1800 applies the DC power after conversion to the charge/dischargecontroller 1206. Thus, the charge/discharge controller 1206 charges thebattery 1207 by using the DC power outputted from the DC/DC converter1800. The DC/DC converter 1800 may be provided with a maximum powerpoint tracking (MPPT) function. MPPT function is a function ofcalculating a combination of values of current and voltage that canmaximize output of the PV 1802.

Further, the electricity-storage system 1200 shown in FIG. 17 may beconfigured as the electricity-storage system 1200 shown in FIG. 19 andthe electricity-storage system 1200 shown in FIG. 18 may be configuredas the electricity-storage system 1200 shown in FIG. 20. An AC/DCconverter 1900, a PV power conditioner 1901, and a PV 1902 in FIG. 19correspond to the AC/DC converter 1700, the PV power conditioner 1701,and the PV 1702 in FIG. 17. Further, a DC/DC converter 2000 and a PV2002 in FIG. 20 correspond to the DC/DC converter 1800 and the PV 1802in FIG. 18.

In other words, the electricity-storage system 1200 may be provided witha switch 1903 and an electrical outlet 1904 as shown in FIG. 19, and theelectricity-storage system 1200 may be provided with a switch 2003 andan electrical outlet 2004 as shown in FIG. 20.

When provided with such configuration, the electricity-storage system1200 can supply power to an electrical device directly from theelectrical outlet 1904 or the electrical outlet 2004. Further, byproviding the switch 1903, 2003, switching between a path from the powerline network to the battery 1207 and a path from the electrical outlet1904, 2004 to the battery 1207 can be performed. According to thisconfiguration that can switch paths, a device connected to the powerline network or the electrical outlet can be sufficiently supplied withpower. In FIGS. 19 and 20, the electrical outlet 1904, 2004 may be avoltage control type of electrical outlet that controls discharge power.Further, the AC plug 1210 may be a voltage control type that controlsdischarge power.

By providing an electrical outlet as shown in FIGS. 19 and 20 to theelectricity-storage system as an output terminal for alternative power,the electricity-storage system can be used as a portable power supplyand convenience of the electricity-storage system is increased.

FIGS. 17 to 20 show PV as an example power generator but the powergenerator is not limited to PV. Power generation may be performed otherthan solar power generation, for example the power generator may be awind power generator or a hydro power generator.

(17) A control program composed of program code for causing a processoror circuits connected to the processor of the electricity-storage systemto execute processing (see FIG. 10) of operations pertaining tocharging/discharging that are indicated in an embodiment above can bestored on a computer-readable non-transitory medium or may bedistributed via communication over various communication channels. Sucha non-transitory medium may be an IC card, a hard disk, an optical disk,a flexible disk, ROM, etc. A control program distributed in this way isused by a processor reading the control program stored on a readablememory, etc., and each function shown in the embodiments is implementedby execution of the control program by the processor.

(18) A control program composed of program code for causing a processoror circuits connected to the processor of the reverse-power monitoringdevice to execute information collection processing (see FIG. 8) ofoperations pertaining to power control (see FIG. 9) that are indicatedin an embodiment above can be stored on a computer-readablenon-transitory medium or may be distributed via communication overvarious communication channels. Such a non-transitory medium may be anIC card, a hard disk, an optical disk, a flexible disk, ROM, etc. Acontrol program distributed in this way is used by a processor readingthe control program stored on a readable memory, etc., and each functionshown in the embodiments is implemented by execution of the controlprogram by the processor.

(19) Each function unit of the reverse-power monitoring device indicatedin an embodiment above may be implemented as a circuit executing thefunction and may be implemented by a program being executed by at leastone processor. Further, the reverse-power monitoring device of anembodiment above may be configured as an integrated circuit (IC), alarge scale integration (LSI), or another integrated circuit package.The package may be incorporated into and made available to variousdevices, and in this way each device can implement each functionindicated in an embodiment.

Each function block is typically implemented as an LSI, which is anintegrated circuit. A function block, a portion of a function block, orall function blocks may be implemented as one chip. LSI is referred tohere, but according to the degree of integration this may be referred toas IC, system LSI, super LSI, or ultra LSI. Further, methods of circuitintegration are not limited to LSI and function blocks may beimplemented by dedicated circuits or general-purpose processors. AfterLSI manufacture, a field programmable gate array (FPGA) orreprogrammable processor that can set and reconfigure circuit cells andconnections within the LSI may be used.

(20) Each function unit of the electricity-storage system indicated inan embodiment above and each functional element indicated in anembodiment above may be implemented as a circuit executing the functionand may be implemented by a program being executed by at least oneprocessor. Further, the electricity-storage system of an embodimentabove may be configured as an integrated circuit (IC), a large scaleintegration (LSI), or another integrated circuit package. The packagemay be incorporated into and made available to various devices, and inthis way each device can implement each function indicated in anembodiment.

Each function block is typically implemented as an LSI, which is anintegrated circuit. A function block, a portion of a function block, orall function blocks may be implemented as one chip. LSI is referred tohere, but according to the degree of integration this may be referred toas IC, system LSI, super LSI, or ultra LSI. Further, methods of circuitintegration are not limited to LSI and function blocks may beimplemented by dedicated circuits or general-purpose processors. AfterLSI manufacture, a field programmable gate array (FPGA) orreprogrammable processor that can set and reconfigure circuit cells andconnections within the LSI may be used.

(21) Embodiments 1 and 2 and each modification may be combined asappropriate.

<Supplement>

An embodiment of the electricity-storage system and the reverse-powermonitoring device pertaining to the present invention and resultsthereof are described below.

(a) The electricity-storage system (110 a) pertaining to the presentinvention is an electricity-storage system comprising: a secondarybattery (304); a connector (310) that is connectable to a power linenetwork; a communicator (301) that communicates with an external device;and a controller (308) that controls discharge so that, when thecommunicator receives an instruction indicating discharge enablement,the power line network is supplied power from the secondary battery viathe connector.

Here, the power line network is downstream of the external device andindicates a closed electrical grid, for example an electrical gridwithin building such as a house or factory.

According to this configuration, the electricity storage system performsdischarging according to the discharge enablement instruction from theexternal device and therefore, when compared to an electricity storagesystem that can freely discharge, the possibility of reverse power flowis reduced, increasing safety when using the electricity storage system.Further, the electricity storage system can be used simply by connectinga plug to an electrical outlet, and therefore has increased conveniencefor users.

(b) The electricity-storage system pertaining to (a), above, may beconfigured so that the communicator executes power line communicationusing the power line network, via the connector.

According to this configuration, the electricity-storage system executescommunication by using power line communication via the power linenetwork and the plug (connector) connected to an electrical outlet, andtherefore a communication route other than the power line network is notrequired.

Further, discharge is executed by using communication via the power linenetwork, and therefore discharge is not executed when the plug is notconnected to the electrical outlet. In a case in which theelectricity-storage system is not connected to the electrical outlet itis not possible to receive instruction, and therefore discharge is notexecuted. Accordingly, the electricity-storage system has a high levelof safety.

(c) The electricity-storage system pertaining to (b), above, may beconfigured so that the external device is disposed upstream of the powerline network and is a monitoring device for monitoring whether or notreverse power flow will occur, the external device has a function ofoutputting an instruction indicating discharge enablement according towhether or not reverse power flow will occur, and the controller doesnot cause discharge when the instruction indicating discharge enablementis not received.

According to this configuration, the electricity-storage system does notexecute discharge without an instruction indicating discharge enablementfrom the reverse-power monitoring device that monitors reverse powerflow, and therefore can ensure that reverse power flow will not occur.

(d) The electricity-storage system pertaining to (c), above, may beconfigured so that the controller, when a reference voltage is beingapplied to the power line network, detects a phase of power flowing tothe power line network and selects a synchronous scheme according towhich power is synchronized to the detected phase and discharged, andwhen a reference voltage is not being applied to the power line network,selects an asynchronous scheme according to which a reference voltage isdischarged.

According to this configuration, the electricity-storage system canexecute discharge both when power from a power company, etc., is alreadybeing supplied to the power line network and when power is not alreadybeing supplied to the power line network. In a case in which power isalready being supplied to the power line network, theelectricity-storage system can synchronize to the power and executedischarge, and therefore contribute to the supply of power.

(e) The electricity-storage system pertaining to (d), above, may beconfigured so that the controller causes discharge according to theasynchronous scheme when the instruction indicating discharge enablementindicates discharge of a reference voltage.

According to this configuration, when the instruction indicatingdischarge enablement instructs discharge of a reference voltage, theelectricity-storage system can execute discharge according to theasynchronous scheme because a reference voltage is not already flowingto the power line network. Synchronous processing can be omitted, andtherefore the processing burden of the electricity-storage system can bereduced.

(f) The electricity-storage system pertaining to (a), above, may beconfigured so that the controller, when the secondary battery isdischarging and a discharge stop instruction is received from theexternal device, causes discharge from the secondary battery to stop.

According to this configuration, the electricity-storage system can stopdischarge according to instruction from the external device. Thus,discharge of excessive power need not be performed.

(g) The electricity-storage system pertaining to (a), above, may furthercomprise a detector that detects whether or not the power line networkis in a state of power stoppage; and a power stoppage informationtransmitter that, when the detector detects that the power line networkis in a state of power stoppage, transmits power stoppage information tothe external device indicating that power stoppage is occurring.

(h) The electricity-storage system pertaining to (a), above, may furthercomprise: a power supply terminal that receives supply of powergenerated by an external power generator; and a charger terminal thatcharges the secondary battery via the power supply terminal by using thepower generated by the external power generator.

Thus, the electricity-storage system can directly receive power from apower generator and therefore during power stoppage theelectricity-storage system can contribute as a long-lasting powersupply.

(i) The electricity-storage system pertaining to (a), above, may furthercomprise: an output terminal other than the connector for connectingexternal equipment in order to supply power from the secondary batteryto the external equipment; and a switch that switches between a path fordischarging power from the connector to the power line network and apath for discharging power from the connector to the external equipment.

Thus, the electricity-storage system is provided with a power outputother than the connector for connecting to the power line network, andbecause the electricity-storage system can supply power directly toexternal equipment without passing through the power line network, theelectricity-storage system can be used as a portable battery.

Further, as the electricity-storage system is provided with a pathconnecting to the external equipment and a path connecting to the powerline network, discharge can be executed appropriately. For example, in acase in which both paths intersected it would be possible for dischargeto the power line network to make discharge to the external equipmentinsufficient, but this configuration eliminates this possibility.

(j) The monitoring device pertaining to the present invention is amonitoring device (100) disposed between an electrical grid and a powerline network downstream of the electrical grid, the monitoring devicecomprising: a communicator (203) that, when an electricity-storagesystem is connected to the power line network via a power supply outlet,executes communication with the electricity-storage system; and acontroller (204) that, via the communicator and the power supply outlet,issues instructions to the electricity-storage system pertaining todischarge to the power line network.

According to this configuration, the monitoring device can issue adischarge instruction to the electricity-storage system connected to thepower line network. By causing discharge by issuing a dischargeinstruction, the monitoring device makes discharge control easy and, asa result, the possibility of reverse power flow is reduced.

(k) The monitoring device pertaining to (j), above, may furthercomprise: a reverse-flow determiner that, when the electricity-storagesystem is connected to the power line network, determines whether or notthere is a possibility of reverse flow occurring, i.e. whether or notthere is a possibility of power discharged from the electricity-storagesystem flowing from the power line network to the electrical grid,wherein the controller, when the reverse-flow determiner determines thatthere is a possibility of reverse flow occurring, instructs anelectricity-storage system that is discharging to stop discharging.

According to this configuration, when there is a possibility of reversepower flow occurring, the monitoring device instructs theelectricity-storage system to stop discharging and therefore occurrenceof reverse power flow is suppressed.

(l) The monitoring device pertaining to (k), above, may be configured sothat the controller is further able to set a physical switch thatphysically switches the electrical grid and the power line networkbetween a connected state and a disconnected state to the disconnectedstate when the reverse-flow determiner determines that there is apossibility of reverse flow occurring.

According to this configuration, the monitoring device can physicallydisconnect the electrical grid from the power line network and therebyreliably prevent reverse power flow in which power flows from the powerline network to the electrical grid.

(m) The monitoring device pertaining to (l), above, may furthercomprise: a power stoppage determiner that determines whether or not theelectrical grid is in a power stoppage state, wherein the reverse-flowdeterminer determines that there is a possibility of reverse flowoccurring when the power stoppage determiner determines that theelectrical grid is in a power stoppage state.

According to this configuration, the monitoring device can detect powerstoppage and thereby prevent reverse power flow. When power stoppageoccurs, potential at the electrical grid decreases, making theoccurrence of reverse power flow more likely, but this configurationprevents the occurrence of reverse power flow when power stoppageoccurs.

(n) The monitoring device pertaining to (m), above, may be configured sothat the controller, after instructing discharging to stop when thereverse-flow determiner determines that there is a possibility ofreverse flow occurring, instructs the electricity-storage system todischarge power to the power line network.

According to this configuration, the monitoring device can, after powerstoppage, instruct the electricity-storage system to discharge, causingpower to be supplied to device connected to the power line networkduring power stoppage.

(o) The monitoring device pertaining to (n), above, may be configured sothat at least one electricity-storage system is connected to the powerline network, and the monitoring device may further comprise anelectricity-storage system information acquirer that acquiresinformation related to a state of charge and a discharge amount of theat least one electricity-storage system connected to the power linenetwork, wherein the controller, when the power stoppage determinerdetermines that power stoppage is occurring, selects one of the at leastone electricity-storage system to cause to discharge, based on the stateof charge and the discharge amount of each of the at least oneelectricity-storage system, and transmits, via the communicator,information for causing the selected one of the at least oneelectricity-storage system to discharge a reference voltage.

According to this configuration, the monitoring device can instruct aselected electricity-storage system to discharge a reference voltageduring power stoppage. Accordingly, when instructing anotherelectricity-storage system to discharge, the monitoring device caninstruct the other electricity-storage system to synchronize to thereference voltage and discharge.

(p) The monitoring device pertaining to (k), above, may furthercomprise: an electricity-storage system information acquirer thatacquires information related to a discharge amount of anelectricity-storage system connected to the power line network; and aload information acquirer that acquires a power consumption amount of aload connected to the power line network, wherein the reverse-flowdeterminer determines that there is a possibility of reverse flowoccurring when the power amount used by the load connected to the powerline network subtracted from the discharge amount of theelectricity-storage system is greater than a power value of theelectrical grid.

According to this configuration, the monitoring device can detect apossibility of reverse power flow and prevent occurrence of reversepower flow.

(q) The monitoring device pertaining to (k), above, may be configured sothat the electricity-storage system is provided in a plurality and theelectricity-storage systems are connected to the power line network, andthe monitoring device may further comprise an electricity-storage systeminformation acquirer that acquires information related to states ofcharge and discharge amounts of the electricity-storage systemsconnected to the power line network, wherein the controller selects anelectricity-storage system from the electricity-storage systems based onthe states of charge and discharge amounts of the electricity-storagesystems and transmits a discharge enablement instruction to the selectedelectricity-storage system.

According to this configuration, even when a plurality of theelectricity-storage systems are connected to the power line network,when a possibility is low of reverse power flow the monitoring devicecan flexibly cause discharge.

(r) The monitoring device pertaining to (k), above, may be configured sothat at least one electricity-storage system is connected to the powerline network, and the controller, upon receiving, via the communicator,information from the at least one electricity-storage system indicatingthat the power line network is in a state of power stoppage, instructsthe at least one electricity-storage system to stop discharge.

According to this configuration, the monitoring device can detect powerstoppage according to information detected from the electricity-storagesystem and therefore can reduce a possibility of reverse power flow byinstructing discharge to stop in accordance with the informationdetected.

(s) The monitoring device pertaining to (r), above, may be configured sothat the controller, after instructing the at least oneelectricity-storage system to stop discharge, selects one of the atleast one electricity-storage system to cause to discharge, based on thestate of charge and the discharge amount of the at least oneelectricity-storage system, and transmits, via the communicator,information for causing the selected one of the at least oneelectricity-storage system to discharge a reference voltage.

According to this configuration, the monitoring device can instruct aselected electricity-storage system to discharge a reference voltageduring power stoppage. Accordingly, when instructing anotherelectricity-storage system to discharge, the monitoring device caninstruct the other electricity-storage system to synchronize to thereference voltage and discharge.

INDUSTRIAL APPLICABILITY

The power control system pertaining to the present invention can be usedas a power system with a low possibility of reverse power flow that canbe used in emergencies such as power stoppages.

REFERENCE SIGNS LIST

-   100 reverse-power monitoring device-   110 a, 110 b electricity-storage system-   120 distribution panel-   121 main breaker-   122 a, 122 b, 122 c breaker-   130 a, 130 b load-   140 a, 140 b, electrical outlet-   150 electrical grid-   160 network-   201 path switcher-   202 detector-   203 communicator-   204 controller-   205 charge/discharge controller-   206 battery-   301 communicator-   302 ACDC inverter-   303 charge controller-   304 battery-   305 DCAC inverter-   306 synchronous/asynchronous unit-   307 switch-   308 controller-   310 plug-   1200 electricity-storage system-   1201 communicator-   1202 switch-   1203 power stoppage detector-   1204 synchronous/asynchronous unit-   1205 bi-directional inverter-   1206 charge/discharge controller-   1207 battery-   1208 controller-   1210 plug-   1700, 1900 AC/DC converter-   1701, 1901 PV power conditioner-   1702, 1802, 1902, 2002 PV-   1800, 2000 DC/DC converter-   1904, 2004 electrical outlet

1. An electricity-storage system comprising: a secondary battery; afirst connector terminal that is electrically connectable to a powerline network; a second connector terminal that is electricallyconnectable to an external device; a switcher that switches a supplydestination for electrical power from the secondary battery between thefirst connector terminal and the second connector terminal; and acontroller that makes the switcher switch to the first connectorterminal and causes discharge from the secondary battery according to asynchronous scheme in which electrical power is discharged synchronizedwith a phase of electrical power flowing in the power line network, andmakes the switcher switch to the second connector terminal and causesdischarge from the secondary battery according to an asynchronous schemein which electrical power is discharged at a reference voltage.
 2. Theelectricity-storage system according to claim 1, wherein the controllermakes the switcher switch to the first connector terminal and causesdischarge from the secondary battery according to the synchronous schemewhen the power line network is not in a state of power outage, and makesthe switcher switch to the second connector terminal and causesdischarge from the secondary battery according to the asynchronousscheme when the power line network is in a state of power outage.
 3. Anoperating method of an electricity-storage system including a secondarybattery, a first connector terminal that is electrically connectable toa power line network, and a second connector terminal that iselectrically connectable to an external device, the operating methodcomprising: switching a supply destination for electrical power from thesecondary battery to the first connector terminal and causing dischargefrom the secondary battery according to a synchronous scheme in whichelectrical power is discharged synchronized with a phase of electricalpower flowing in the power line network; and switching the supplydestination for electrical power from the secondary battery to thesecond connector terminal and causing discharge from the secondarybattery according to an asynchronous scheme in which electrical power isdischarged at a reference voltage.
 4. The operating method according toclaim 3, wherein the switching of the supply destination to the firstconnector terminal and the causing of discharge according to thesynchronous scheme are executed when the power line network is not in astate of power outage, and the switching of the supply destination tothe second connector terminal and the causing of discharge according tothe asynchronous scheme are executed when the power line network is in astate of power outage.